The present invention relates to impregnating wood, and more particularly the present invention relates to a method for preparing a piece of wood for purposes of impregnating it with a material to protect the wood against parasites and other dangerous insects, as well as, or alternatively, for rendering the wood flame retardant.
It is generally known to treat pieces of wood with an impregnating material so as to protect them against parasites such as termites, or the like, fungus, etc. It is also known to impregnate wood so as to render it inflammable or at least flame retardant. Generally speaking, it is known to provide such impregnation by dipping the wood into a tank filled with the impregnating liquid, or by brushing the liquid onto the surface, or spraying the piece of wood with the impregnating material. Of course different brands and kinds of wood differ considerably with regard to their ability to permit penetration of liquid into the texture of the material. In some instances, the texture is so dense that deep penetration is practically prevented. In such a situation, it has been the practice to force the impregnating medium by means of an autoclave into the wood. However, even in an autoclave fir wood permits a penetration transversely to the fiber of, at the most, about 1 mm deep, which is not sufficient.
Independently from the foregoing, it is known to perforate the surface of a piece of wood by means of rolls having pins or cutters arranged along the periphery. A treatment of a piece of wood with such a roll serves the purpose of preparing the piece to permit deeper impregnation of the material. In practice, penetration depth up to 10 mms can be obtained. It was found, however, that on account of the bending moment acting on the pins or pricks used to penetrate into the wood, the surface of the wood suffers, and particularly the surface near fibers are torn. This then means that the wood loses strength. Also, from an overall point of view the surface of the wood appears quite torn and so they cannot be used anymore for decorative purposes, for example, paneling or the like.
Another known method for perforating the surface of the wood uses rotating pins. That practice was found to be disadvantageous, however, as the pins may and do break. This is particularly the case when such a pin or needle hits a knot in the wood. It is well known that knots resist very heavily any kind of penetration which in turn means that the needles will wear heavily and may be heated. Of course, they may even break.